# Low-Fat Cheddar Cheese Influences Gut Microbiota Composition and Diversity in Human Microbiota–Associated Mice

## TL;DR

Low-fat Cheddar cheese changes gut bacteria in mice, increasing diversity and probiotic-like bacteria.

## Contribution

First experimental evidence showing whole low-fat Cheddar cheese affects human-like gut microbiota in mice.

## Key findings

- Cheese-fed mice had higher gut microbial diversity compared to control mice.
- Lactococcus and Streptococcus bacteria from cheese increased in the gut microbiota.
- Cheese altered the ratio of Firmicutes to Bacteroidetes in the gut.

## Abstract

Cheese is one of the most widely consumed fermented dairy foods, yet there is limited experimental evidence on how it influences the gut microbiota. Most previous studies have relied on population surveys or on testing isolated cheese components, rather than cheese as a whole food. In this study, we investigated how daily consumption of low-fat Cheddar cheese affects the gut microbiota using a specialized mouse model colonized with human intestinal bacteria. Human microbiota–associated mice were fed either a standard diet or a diet containing low-fat Cheddar cheese for six weeks. We found that cheese consumption significantly changed the structure and diversity of the gut microbial community. The cheese-fed mice showed an increase in overall bacterial diversity and a greater abundance of Lactococcus and Streptococcus microorganisms naturally present in cheese and known for their potential probiotic properties. These results suggest that cheese, when included as part of a balanced diet, can beneficially influence the gut microbiota. However, because this work was conducted in an animal model, further clinical studies are required to confirm whether similar effects occur in humans.

Cheese is a complex fermented dairy food containing bioactive nutrients and microorganisms that can influence host physiology. However, most existing evidence of its health effects derives from observational studies or investigations of isolated components rather than the whole food matrix. The present study examined the impact of low-fat Cheddar cheese as a whole food on the gut microbiota using a human microbiota–associated (HMA) mouse model. Germ-free C57BL/6 mice were colonized with human fecal microbiota and randomly assigned to either a control diet or a diet supplemented with low-fat Cheddar cheese (7.5% w/w) for six weeks. Fecal samples were collected longitudinally and analyzed by 16S rRNA gene (V3–V4 region) amplicon sequencing. Human microbiota transplantation successfully established a stable, human-like gut microbial community in the mice. Cheese supplementation significantly increased alpha diversity (Shannon and Chao1 indices) and altered microbial composition, characterized by a higher relative abundance of Firmicutes and a reduction in Bacteroidetes (p < 0.001). At the genus level, Lactococcus and Streptococcus were enriched in cheese-fed mice, reflecting potential viable transfer of cheese-derived lactic acid bacteria. These findings provide experimental evidence that low-fat Cheddar cheese can beneficially influence the human-derived gut microbiota in an animal model and highlight the need for further clinical research to validate these effects in humans.